Stone Pine(Pinus pinea L.)is currently the pine species with the highest commercial value with edible seeds.In this respect,this study introduces a new methodology for extracting Stone Pine trees from Digital Surface ...Stone Pine(Pinus pinea L.)is currently the pine species with the highest commercial value with edible seeds.In this respect,this study introduces a new methodology for extracting Stone Pine trees from Digital Surface Models(DSMs)generated through an Unmanned Aerial Vehicle(UAV)mission.We developed a novel enhanced probability map of local maxima that facilitates the computation of the orientation symmetry by means of new probabilistic local minima information.Four test sites are used to evaluate our automated framework within one of the most important Stone Pine forest areas in Antalya,Turkey.A Hand-held Mobile Laser Scanner(HMLS)was utilized to collect the reference point cloud dataset.Our findings confirm that the proposed methodology,which uses a single DSM as an input,secures overall pixel-based and object-based F1-scores of 88.3%and 97.7%,respectively.The overall median Euclidean distance revealed between the automatically extracted stem locations and the manually extracted ones is computed to be 36 cm(less than 4 pixels),demonstrating the effectiveness and robustness of the proposed methodology.Finally,the comparison with the state-of-the-art reveals that the outcomes of the proposed methodology outperform the results of six previous studies in this context.展开更多
As a GIS tool,visibility analysis is used in many areas to evaluate both visible and non-visible places.Visibility analysis builds on a digital surface model describing the terrain morphology,including the position an...As a GIS tool,visibility analysis is used in many areas to evaluate both visible and non-visible places.Visibility analysis builds on a digital surface model describing the terrain morphology,including the position and shapes of all objects that can sometimes act as visibility barriers.However,some barriers,for example vegetation,may be permeable to a certain degree.Despite extensive research and use of visibility analysis in different areas,standard GIS tools do not take permeability into account.This article presents a new method to calculate visibility through partly permeable obstacles.The method is based on a quasi-Monte Carlo simulation with 100 iterations of visibility calculation.Each iteration result represents 1%of vegetation permeability,which can thus range from 1%to 100%visibility behind vegetation obstacles.The main advantage of the method is greater accuracy of visibility results and easy implementation on any GIS software.The incorporation of the proposed method in GIS software would facilitate work in many fields,such as architecture,archaeology,radio communication,and the military.展开更多
The accuracy of Digital Surface Models(DSMs)generated using stereo matching methods varies due to the varying acquisition conditions and configuration parameters of stereo images.It has been a good practice to fuse th...The accuracy of Digital Surface Models(DSMs)generated using stereo matching methods varies due to the varying acquisition conditions and configuration parameters of stereo images.It has been a good practice to fuse these DSMs generated from various stereo pairs to achieve enhanced,in which multiple DSMs are combined through computational approaches into a single,more accurate,and complete DSM.However,accurately characterizing detailed objects and their boundaries still present a challenge since most boundary-ware fusion methods still struggle to achieve sharpened depth discontinuities due to the averaging effects of different DSMs.Therefore,we propose a simple and efficient adaptive image-guided DSM fusion method that applies k-means clustering on small patches of the orthophoto to guide the pixel-level fusion adapted to the most consistent and relevant elevation points.The experiment results show that our proposed method has outperformed comparing methods in accuracy and the ability to preserve sharpened depth edges.展开更多
A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface...A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface model was generated with image matching. The elevation model representing the terrain surface, a ‘digital terrain model’,was extracted from the digital surface model using morphological filtering. Individual trees were extracted by analyzing elevation flow on the digital elevation model because the elevation reached the highest value on the tree peaks compared to the neighborhood elevation pixels. The quality of the results was assessed by comparison with reference data for correctness of the estimated number of trees. The tree heights were calculated and evaluated with ground truth dataset. The results showed 80% correctness and 90% completeness.展开更多
It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface.On the basis of the architectural survey project of"Chilin Nunnery Reconstruction",t...It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface.On the basis of the architectural survey project of"Chilin Nunnery Reconstruction",this paper investigates an easy and feasible way,that is,on project site,applying digital close range photogrammetry and CAD technique to establish the DSM for simulating ancient architectures with complex surface.The method has been proved very effective in practice.展开更多
In modern terrain-following guidance it is an important index for flight vehicle to cruise about safely and normally. On the basis of a constructing method of digital surface model (DSM), the definition, classificatio...In modern terrain-following guidance it is an important index for flight vehicle to cruise about safely and normally. On the basis of a constructing method of digital surface model (DSM), the definition, classification and scale analysis of an isolated obstacle threatening flight safety of terrain-following guidance are made. When the interval of vertical-and cross-sections on DSM is 12. 5 m, the proportion of isolated obstacles to the data amount of DSM model to be loaded is optimal. The main factors influencing the lowest flying height in terrain-following guidance are analyzed, and a primary safe criterion of the lowest flying height over DSM model is proposed. According to their test errors, the lowest flying height over 1:10 000 DSM model can reach 40. 5 m^45. 0 m in terrain-following guidance. It is shown from the simulation results of a typical urban district that the proposed models and methods are reasonable and feasible.展开更多
The problem of taking an unorganized point cloud in 3D space and fitting a polyhedral surface to those points is both important and difficult. Aiming at increasing applications of full three dimensional digital terrai...The problem of taking an unorganized point cloud in 3D space and fitting a polyhedral surface to those points is both important and difficult. Aiming at increasing applications of full three dimensional digital terrain surface modeling, a new algorithm for the automatic generation of three dimensional triangulated irregular network from a point cloud is pro- posed. Based on the local topological consistency test, a combined algorithm of constrained 3D Delaunay triangulation and region-growing is extended to ensure topologically correct reconstruction. This paper also introduced an efficient neighbor- ing triangle location method by making full use of the surface normal information. Experimental results prove that this algo- rithm can efficiently obtain the most reasonable reconstructed mesh surface with arbitrary topology, wherein the automati- cally reconstructed surface has only small topological difference from the true surface. This algorithm has potential applica- tions to virtual environments, computer vision, and so on.展开更多
A DEM （digital elevation model） was once used to calculate viewsheds in the early days of GIS applications. The emergence of LiDAR （light detection and ranging） data which are likely to have higher spatial resolut...A DEM （digital elevation model） was once used to calculate viewsheds in the early days of GIS applications. The emergence of LiDAR （light detection and ranging） data which are likely to have higher spatial resolutions than traditional DEMs contributed to the improvements of calculation accuracy greatly. The objective of this study is to validate that the LiDAR data calculate and predict a viewshed better than the traditional low-resolution DEMs with 10 m and 30 m spatial resolutions. Using digital terrain data acquired for part of the Nez Perce National Forest in Idaho, calculation accuracy for viewsheds was scrutinized in depth. Four hundred and eighty four （484） observation points were selected randomly to compute viewsheds from the 1-m pixel, bare-earth LiDAR data and from the traditional 10 m and 30 m DEMs. The comparison of their RMSEs （root-mean-squared-error） values proves the newer generation of digital terrain data produces more accurate viewsheds than ones generated from the traditional DEMs. Analyses of variance and t-tests show the viewsheds calculated from various terrain models are statistically different. Therefore, findings from this study suggest that high-quality LiDAR data, if available, should be used for decision-making in planning for and the management of the scenic resources.展开更多
In many cases,the Digital Surface Models(DSMs)and Digital Elevation Models(DEMs)are obtained with Light Detection and Ranging(LiDAR)or stereo matching.As an active method,LiDAR is very accurate but expensive,thus ofte...In many cases,the Digital Surface Models(DSMs)and Digital Elevation Models(DEMs)are obtained with Light Detection and Ranging(LiDAR)or stereo matching.As an active method,LiDAR is very accurate but expensive,thus often limiting its use in small-scale acquisition.Stereo matching is suitable for large-scale acquisition of terrain information as the increase of satellite stereo sensors.However,underperformance of stereo matching easily occurs in textureless areas.Accordingly,this study proposed a Shading Aware DSM GEneration Method(SADGE)with high resolution multi-view satellite images.Considering the complementarity of stereo matching and Shape from Shading(SfS),SADGE combines the advantage of stereo matching and SfS technique.First,an improved Semi-Global Matching(SGM)technique is used to generate an initial surface expressed by a DSM;then,it is refined by optimizing the objective function which modeled the imaging process with the illumination,surface albedo,and normal object surface.Different from the existing shading-based DEM refinement or generation method,no information about the illumination or the viewing angle is needed while concave/convex ambiguity can be avoided as multi-view images are utilized.Experiments with ZiYuan-3 and GaoFen-7 images show that the proposed method can generate higher accuracy DSM(12.5-56.3%improvement)with sound overall shape and temporarily detailed surface compared with a software solution(SURE)for multi-view stereo.展开更多
OpenStreetMap(OSM)currently represents the most popular project of Volunteered Geographic Information(VGI):geodata are collected by common people and made available for public use.Airborne Laser Scanning(ALS)enables t...OpenStreetMap(OSM)currently represents the most popular project of Volunteered Geographic Information(VGI):geodata are collected by common people and made available for public use.Airborne Laser Scanning(ALS)enables the acquisition of high-resolution digital elevation models that are used for many applications.This study combines the advantages of both ALS and OSM,offering a promising new approach that enhances data quality and allows change detection:the mainly up-to-date 2D data of OSM can be combined with the high-resolution–but rarely updated–elevation information provided by ALS.This case study investigates building objects of OSM and ALS data of the city of Bregenz,Austria.Data quality of OSM is discerned by the comparison of building footprints using different true positive definitions(e.g.overlapping area).High quality of OSM data is revealed,yet also limitations of each method with respect to heterogeneous regions and building outlines are identified.For the first time,an up-to-date Digital Surface Model(DSM)combining 2D OSM and ALS data is achieved.A multitude of applications such as flood simulations and solar potential assessments can directly benefit from this data combination,since their value and reliability strongly depend on an up-to-date DSM.展开更多
The accuracy of topographic correction of Landsat data based on a Digital Surface Model(DSM)depends on the quality,scale and spatial resolution of the DSM data used and the co-registration between the DSM and the sate...The accuracy of topographic correction of Landsat data based on a Digital Surface Model(DSM)depends on the quality,scale and spatial resolution of the DSM data used and the co-registration between the DSM and the satellite image.A physics-based bidirectional reflectance distribution function(BRDF)and atmospheric correction model in conjunction with a 1-second DSM was used to conduct the analysis in this paper.The results show that for the examples used from Australia,the 1-second DSM,can provide an effective product for this task.However,it was found that some remaining artefacts in the DSM data,originally due to radar shadow,can still cause significant local errors in the correction.Where they occur,false shadows and over-corrected surface reflectance factors can be observed.More generally,accurate co-registration between satellite images and DSM data was found to be critical for effective correction.Mis-registration by one or two pixels could lead to large errors of retrieved surface reflectance factors in gully and ridge areas.Using low-resolution DSM data in conjunction with high-resolution satellite images will also fail to correct significant terrain components where they occur at the finer scales of the satellite images.DSM resolution appropriate to the resolution of satellite image and the roughness of the terrain is needed for effective results,and the rougher the terrain,the more critical will be the accurate registration.展开更多
Targeting at a reliable image matching of multiple remote sensing images for the generation of digital surface models,this paper presents a geometric-constrained multi-view image matching method,based on an energy min...Targeting at a reliable image matching of multiple remote sensing images for the generation of digital surface models,this paper presents a geometric-constrained multi-view image matching method,based on an energy minimization framework.By employing a geometrical constraint,the cost value of the energy function was calculated from multiple images,and the cost value was aggregated in an image space using a semi-global optimization approach.A homography transform parameter calculation method is proposed for fast calculation of projection pixel on each image when calculation cost values.It is based on the known interior orientation parameters,exterior orientation parameters,and a given elevation value.For an efficient and reliable processing of multiple remote sensing images,the proposed matching method was performed via a coarse-to-fine strategy through image pyramid.Three sets of airborne remote sensing images were used to evaluate the performance of the proposed method.Results reveal that the multi-view image matching can improve matching reliability.Moreover,the experimental results show that the proposed method performs better than traditional methods.展开更多
One of the challenges of remote sensing and computer vision lies in the three-dimensional(3-D)reconstruction of individual trees by using automated methods through very high-resolution(VHR)data sets.However,a successf...One of the challenges of remote sensing and computer vision lies in the three-dimensional(3-D)reconstruction of individual trees by using automated methods through very high-resolution(VHR)data sets.However,a successful and complete 3-D reconstruction relies on precise delineation of the trees in two dimensions.In this paper,we present an original approach to detect and delineate citrus trees using unmanned aerial vehicles based on photogrammetric digital surface models(DSMs).The symmetry of the citrus trees in a DSM is handled by an orientationbased radial symmetry transform which is computed in a unique way.Next,we propose an efficient strategy to accurately build influence regions of each tree,and then we delineate individual citrus trees through active contours by taking into account the influence region of each canopy.We also present two efficient strategies to filter out erroneously detected canopy regions without having any height thresholds.Experiments are carried out on eight test DSMs composed of different types of citrus orchards with varying densities and canopy sizes.Extensive comparisons to the state-of-the-art approaches reveal that our proposed approach provides superior detection and delineation performances through supporting a nice balance between precision and recall measures.展开更多
Accurate data acquisition and analysis to obtain crop canopy information are critical steps to understand plant growth dynamics and to assess the potential impacts of biotic or abiotic stresses on plant development.A ...Accurate data acquisition and analysis to obtain crop canopy information are critical steps to understand plant growth dynamics and to assess the potential impacts of biotic or abiotic stresses on plant development.A versatile and easy to use monitoring system will allow researchers and growers to improve the follow-up management strategies within farms once potential problems have been detected.This study reviewed existing remote sensing platforms and relevant information applied to crops and specifically grapevines to equip a simple Unmanned Aerial Vehicle(UAV)using a visible high definition RGB camera.The objective of the proposed Unmanned Aerial System(UAS)was to implement a Digital Surface Model(DSM)in order to obtain accurate information about the affected or missing grapevines that can be attributed to potential biotic or abiotic stress effects.The analysis process started with a three-dimensional(3D)reconstruction from the RGB images collected from grapevines using the UAS and the Structure from Motion(SfM)technique to obtain the DSM applied on a per-plant basis.Then,the DSM was expressed as greyscale images according to the halftone technique to finally extract the information of affected and missing grapevines using computer vision algorithms based on canopy cover measurement and classification.To validate the automated method proposed,each grapevine row was visually inspected within the study area.The inspection was then compared to the digital assessment using the proposed UAS in order to validate calculations of affected and missing grapevines for the whole studied vineyard.Results showed that the percentage of affected and missing grapevines was 9.5%and 7.3%,respectively from the area studied.Therefore,for this specific study,the abiotic stress that affected the experimental vineyard(frost)impacted a total of 16.8%of plants.This study provided a new method for automatically surveying affected or missing grapevines in the field and an evaluation tool for plant growth conditions,which can be implemented for other uses such as canopy management,irrigation scheduling and other precision agricultural applications.展开更多
Information about canopy vigor and growth are critical to assess the potential impacts of biotic or abiotic stresses on plant development.By implementing a Digital Surface Model(DSM)to imagery obtained using Unmanned ...Information about canopy vigor and growth are critical to assess the potential impacts of biotic or abiotic stresses on plant development.By implementing a Digital Surface Model(DSM)to imagery obtained using Unmanned Aerial Vehicles(UAV),it is possible to filter canopy information effectively based on height,which provides an efficient method to discriminate canopy from soil and lower vegetation such as weeds or cover crops.This paper describes a method based on the DSM to assess canopy growth(CG)as well as missing plants from a kiwifruit orchard on a plant-by-plant scale.The DSM was initially extracted from the overlapping RGB aerial imagery acquired over the kiwifruit orchard using the Structure from Motion(SfM)algorithm.An adaptive threshold algorithm was implemented using the height difference between soil/lower plants and kiwifruit canopies to identify plants and extract canopy information on a non-regular surface.Furthermore,a customized algorithm was developed to discriminate single kiwifruit plants automatically,which allowed the estimation of individual canopy cover fractions(fc).By applying differential fc thresholding,four categories of the CG were determined automatically:(i)missing plants;(ii)low vigor;(iii)moderate vigor;and(iv)vigorous.Results were validated by a detailed visual inspection on the ground,which rendered an overall accuracy of 89.5%for the method proposed to assess CG at the plant-by-plant level.Specifically,the accuracies for CG category(i)-(iv)were 94.1%,85.1%,86.7%,and 88.0%,respectively.The proposed method showed also to be appropriate to filter out weeds and other smaller non-plant materials which are extremely difficult to be distinguished by common colour thresholding or edge identification methods.展开更多
Segmentation and edge regulation are studied deeply to extract buildings fromDSM data produced in this paper. Building segmentation is the first step to extract buildings, anda new segmentation method-adaptive iterati...Segmentation and edge regulation are studied deeply to extract buildings fromDSM data produced in this paper. Building segmentation is the first step to extract buildings, anda new segmentation method-adaptive iterative segmentation considering rati-o mean square-is proposedto extract the contour of buildings effectively. A sub-image (such as 50X50 pixels) of the image isprocessed in sequence, the average gray level and its ratio mean square are calculated first, thenthreshold of the sub-image is selected by using iterative threshold segmentation. The current pixelis segmented according to the threshold, the average gray level and the ratio mean square of thesub-image. The edge points of the building are grouped according to the azimuth of neighbor points,and then the optimal azimuth of the points that belong to the same group can be calculated by usingline interpolation.展开更多
In photogrammetry and remote sensing,image matching is a basic and crucial process for automatic DEM generation.In this paper we presented a image relaxation matching method based on feature points.This method can be ...In photogrammetry and remote sensing,image matching is a basic and crucial process for automatic DEM generation.In this paper we presented a image relaxation matching method based on feature points.This method can be considered as an extention of regular grid point based matching.It avoids the shortcome of grid point based matching.For example,with this method,we can avoid low or even no texture area where errors frequently appear in cross correlaton matching.In the mean while,it makes full use of some mature techniques such as probability relaxation,image pyramid and the like which have already been successfully used in grid point matching process.Application of the technique to DEM generaton in different regions proved that it is more reasonable and reliable.展开更多
A novel method for multi-image matching by synthesizing image and object-space information is proposed. Firstly, four levels of image pyramids are generated according to the rule that the next pyramid level is generat...A novel method for multi-image matching by synthesizing image and object-space information is proposed. Firstly, four levels of image pyramids are generated according to the rule that the next pyramid level is generated from the previous level using the average gray values of the 3 by 3 pixels, and the first level of pyramid image is generated from the original image. The initial horizontal parallaxes between the reference image and each searching image are calculated at the highest level of the image pyramid. Secondly, corresponding image points are searched in each stereo image pair from the third level of image pyramid, and the matching results in all stereo pairs are integrated in the object space, by which the mismatched image points can be eliminated and more accurate spatial information can be obtained for the subsequent pyramid image matching. The matching method based on correlation coefficient with geometric constraints and global relaxation matching is introduced in the process of image matching. Finally, the feasibility of the method proposed in this paper is verified by the experiments using a set of digital frame aerial images with big overlap. Compared with the traditional image matching method with two images, the accuracy of the digital surface model (DSM) generated using the proposed method shows that the multiimage matching method can eliminate the mismatched points effectively and can improve the matching success rate significantly.展开更多
Planation surface, a surface that is almost flat, is a kind of low-relief landforms. Planation surface is the consequence of the denudation and planation processes under a tectonic stable condition. The quantitative e...Planation surface, a surface that is almost flat, is a kind of low-relief landforms. Planation surface is the consequence of the denudation and planation processes under a tectonic stable condition. The quantitative expression of the characteristics of planation surface plays a key role in reconstructing and describing the evolutionary process of landforms. In this study, Landform Planation Index(LPI), a new terrain derivative, was proposed to quantify the characteristics of planation surface. The LPIs were calculated based on the summit surfaces formed according to the clustering results of peaks. Ten typical areas in the Ordos Platform located in the central part of the Loess Plateau of China are chosen as the test areas for investigating their planation characteristics with the LPI. The experimental results indicate that the LPI can be effectively used to quantify the characteristics of planation surfaces. In addition, the LPI can be further used to depict the patterns of spatial differentiation in the Ordos Platform. Although the present Ordos Platform area is full of the high-density gullies, its planation characteristics is found to be well preserved. Furthermore, the characteristics of the planation surfaces can also reflect the original morphology of the Ordos Platform before the loess dusts deposition process evolved in this area. The statistical results of the LPI show that there is a gradually increasing tendency along with the increasing of slope gradient of summit surface. It indicates that the characteristics of planation surfaces vary among test areas with different landforms. These findings help to deepen the understanding of planation characteristics of the loess landform and its underlying paleotopography. Results of this study can be also served as an important theoretical reference value for revealing the evolutionary process of loess landform.展开更多
The growing demand for current and precise geographic information that pertains to urban areas has given rise to a significant interest in digital surface models that exhibit a high level of detail. Traditional method...The growing demand for current and precise geographic information that pertains to urban areas has given rise to a significant interest in digital surface models that exhibit a high level of detail. Traditional methods for creating digital surface models are insufficient to reflect the details of earth’s features. These models only represent three-dimensional objects in a single texture and fail to offer a realistic depiction of the real world. Furthermore, the need for current and precise geographic information regarding urban areas has been increasing significantly. This study proposes a new technique to address this problem, which involves integrating remote sensing, Geographic Information Systems (GIS), and Architecture Environment software environments to generate a detailed three-dimensional model. The processing of this study starts with: 1) Downloading high-resolution satellite imagery; 2) Collecting ground truth datasets from fieldwork; 3) Imaging nose removing; 4) Generating a Two-dimensional Model to create a digital surface model in GIS using the extracted building outlines; 5) Converting the model into multi-patch layers to construct a 3D model for each object separately. The results show that the 3D model obtained through this method is highly detailed and effective for various applications, including environmental studies, urban development, expansion planning, and shape understanding tasks.展开更多
基金supported by the Projects of Scientific Investigation(BAP)of Ankara Haci Bayram Veli University[Grant No.01/2019-32].
文摘Stone Pine(Pinus pinea L.)is currently the pine species with the highest commercial value with edible seeds.In this respect,this study introduces a new methodology for extracting Stone Pine trees from Digital Surface Models(DSMs)generated through an Unmanned Aerial Vehicle(UAV)mission.We developed a novel enhanced probability map of local maxima that facilitates the computation of the orientation symmetry by means of new probabilistic local minima information.Four test sites are used to evaluate our automated framework within one of the most important Stone Pine forest areas in Antalya,Turkey.A Hand-held Mobile Laser Scanner(HMLS)was utilized to collect the reference point cloud dataset.Our findings confirm that the proposed methodology,which uses a single DSM as an input,secures overall pixel-based and object-based F1-scores of 88.3%and 97.7%,respectively.The overall median Euclidean distance revealed between the automatically extracted stem locations and the manually extracted ones is computed to be 36 cm(less than 4 pixels),demonstrating the effectiveness and robustness of the proposed methodology.Finally,the comparison with the state-of-the-art reveals that the outcomes of the proposed methodology outperform the results of six previous studies in this context.
基金This work was financially supported by project 133/2016/RPP-TO-1/b“Teaching of advanced techniques for geodata processing for follow-up study of geoinformatics”.
文摘As a GIS tool,visibility analysis is used in many areas to evaluate both visible and non-visible places.Visibility analysis builds on a digital surface model describing the terrain morphology,including the position and shapes of all objects that can sometimes act as visibility barriers.However,some barriers,for example vegetation,may be permeable to a certain degree.Despite extensive research and use of visibility analysis in different areas,standard GIS tools do not take permeability into account.This article presents a new method to calculate visibility through partly permeable obstacles.The method is based on a quasi-Monte Carlo simulation with 100 iterations of visibility calculation.Each iteration result represents 1%of vegetation permeability,which can thus range from 1%to 100%visibility behind vegetation obstacles.The main advantage of the method is greater accuracy of visibility results and easy implementation on any GIS software.The incorporation of the proposed method in GIS software would facilitate work in many fields,such as architecture,archaeology,radio communication,and the military.
基金John Hopkins University Applied Physics Lab to support the Imagery of the 2019 DFC datasets
文摘The accuracy of Digital Surface Models(DSMs)generated using stereo matching methods varies due to the varying acquisition conditions and configuration parameters of stereo images.It has been a good practice to fuse these DSMs generated from various stereo pairs to achieve enhanced,in which multiple DSMs are combined through computational approaches into a single,more accurate,and complete DSM.However,accurately characterizing detailed objects and their boundaries still present a challenge since most boundary-ware fusion methods still struggle to achieve sharpened depth discontinuities due to the averaging effects of different DSMs.Therefore,we propose a simple and efficient adaptive image-guided DSM fusion method that applies k-means clustering on small patches of the orthophoto to guide the pixel-level fusion adapted to the most consistent and relevant elevation points.The experiment results show that our proposed method has outperformed comparing methods in accuracy and the ability to preserve sharpened depth edges.
基金financially supported by the scientific research projects coordination unit of Akdeniz University,Project No.FBA-2015-446
文摘A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface model was generated with image matching. The elevation model representing the terrain surface, a ‘digital terrain model’,was extracted from the digital surface model using morphological filtering. Individual trees were extracted by analyzing elevation flow on the digital elevation model because the elevation reached the highest value on the tree peaks compared to the neighborhood elevation pixels. The quality of the results was assessed by comparison with reference data for correctness of the estimated number of trees. The tree heights were calculated and evaluated with ground truth dataset. The results showed 80% correctness and 90% completeness.
文摘It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface.On the basis of the architectural survey project of"Chilin Nunnery Reconstruction",this paper investigates an easy and feasible way,that is,on project site,applying digital close range photogrammetry and CAD technique to establish the DSM for simulating ancient architectures with complex surface.The method has been proved very effective in practice.
基金This project was supported by the National Natural Science Foundation of China (60072009).
文摘In modern terrain-following guidance it is an important index for flight vehicle to cruise about safely and normally. On the basis of a constructing method of digital surface model (DSM), the definition, classification and scale analysis of an isolated obstacle threatening flight safety of terrain-following guidance are made. When the interval of vertical-and cross-sections on DSM is 12. 5 m, the proportion of isolated obstacles to the data amount of DSM model to be loaded is optimal. The main factors influencing the lowest flying height in terrain-following guidance are analyzed, and a primary safe criterion of the lowest flying height over DSM model is proposed. According to their test errors, the lowest flying height over 1:10 000 DSM model can reach 40. 5 m^45. 0 m in terrain-following guidance. It is shown from the simulation results of a typical urban district that the proposed models and methods are reasonable and feasible.
基金Supported by the National Natural Science Foundation of China （No.40671158）, the National 863 Program of China（No.2006AA12Z224） and the Program for New Century Excellent Talents in University （No.NCET-05-0626）.
文摘The problem of taking an unorganized point cloud in 3D space and fitting a polyhedral surface to those points is both important and difficult. Aiming at increasing applications of full three dimensional digital terrain surface modeling, a new algorithm for the automatic generation of three dimensional triangulated irregular network from a point cloud is pro- posed. Based on the local topological consistency test, a combined algorithm of constrained 3D Delaunay triangulation and region-growing is extended to ensure topologically correct reconstruction. This paper also introduced an efficient neighbor- ing triangle location method by making full use of the surface normal information. Experimental results prove that this algo- rithm can efficiently obtain the most reasonable reconstructed mesh surface with arbitrary topology, wherein the automati- cally reconstructed surface has only small topological difference from the true surface. This algorithm has potential applica- tions to virtual environments, computer vision, and so on.
文摘A DEM （digital elevation model） was once used to calculate viewsheds in the early days of GIS applications. The emergence of LiDAR （light detection and ranging） data which are likely to have higher spatial resolutions than traditional DEMs contributed to the improvements of calculation accuracy greatly. The objective of this study is to validate that the LiDAR data calculate and predict a viewshed better than the traditional low-resolution DEMs with 10 m and 30 m spatial resolutions. Using digital terrain data acquired for part of the Nez Perce National Forest in Idaho, calculation accuracy for viewsheds was scrutinized in depth. Four hundred and eighty four （484） observation points were selected randomly to compute viewsheds from the 1-m pixel, bare-earth LiDAR data and from the traditional 10 m and 30 m DEMs. The comparison of their RMSEs （root-mean-squared-error） values proves the newer generation of digital terrain data produces more accurate viewsheds than ones generated from the traditional DEMs. Analyses of variance and t-tests show the viewsheds calculated from various terrain models are statistically different. Therefore, findings from this study suggest that high-quality LiDAR data, if available, should be used for decision-making in planning for and the management of the scenic resources.
基金supported by the National Natural Science Foundation of China[grant number 41801390]the National Key R&D Program of China[grant number 2018YFD1100405].
文摘In many cases,the Digital Surface Models(DSMs)and Digital Elevation Models(DEMs)are obtained with Light Detection and Ranging(LiDAR)or stereo matching.As an active method,LiDAR is very accurate but expensive,thus often limiting its use in small-scale acquisition.Stereo matching is suitable for large-scale acquisition of terrain information as the increase of satellite stereo sensors.However,underperformance of stereo matching easily occurs in textureless areas.Accordingly,this study proposed a Shading Aware DSM GEneration Method(SADGE)with high resolution multi-view satellite images.Considering the complementarity of stereo matching and Shape from Shading(SfS),SADGE combines the advantage of stereo matching and SfS technique.First,an improved Semi-Global Matching(SGM)technique is used to generate an initial surface expressed by a DSM;then,it is refined by optimizing the objective function which modeled the imaging process with the illumination,surface albedo,and normal object surface.Different from the existing shading-based DEM refinement or generation method,no information about the illumination or the viewing angle is needed while concave/convex ambiguity can be avoided as multi-view images are utilized.Experiments with ZiYuan-3 and GaoFen-7 images show that the proposed method can generate higher accuracy DSM(12.5-56.3%improvement)with sound overall shape and temporarily detailed surface compared with a software solution(SURE)for multi-view stereo.
文摘OpenStreetMap(OSM)currently represents the most popular project of Volunteered Geographic Information(VGI):geodata are collected by common people and made available for public use.Airborne Laser Scanning(ALS)enables the acquisition of high-resolution digital elevation models that are used for many applications.This study combines the advantages of both ALS and OSM,offering a promising new approach that enhances data quality and allows change detection:the mainly up-to-date 2D data of OSM can be combined with the high-resolution–but rarely updated–elevation information provided by ALS.This case study investigates building objects of OSM and ALS data of the city of Bregenz,Austria.Data quality of OSM is discerned by the comparison of building footprints using different true positive definitions(e.g.overlapping area).High quality of OSM data is revealed,yet also limitations of each method with respect to heterogeneous regions and building outlines are identified.For the first time,an up-to-date Digital Surface Model(DSM)combining 2D OSM and ALS data is achieved.A multitude of applications such as flood simulations and solar potential assessments can directly benefit from this data combination,since their value and reliability strongly depend on an up-to-date DSM.
文摘The accuracy of topographic correction of Landsat data based on a Digital Surface Model(DSM)depends on the quality,scale and spatial resolution of the DSM data used and the co-registration between the DSM and the satellite image.A physics-based bidirectional reflectance distribution function(BRDF)and atmospheric correction model in conjunction with a 1-second DSM was used to conduct the analysis in this paper.The results show that for the examples used from Australia,the 1-second DSM,can provide an effective product for this task.However,it was found that some remaining artefacts in the DSM data,originally due to radar shadow,can still cause significant local errors in the correction.Where they occur,false shadows and over-corrected surface reflectance factors can be observed.More generally,accurate co-registration between satellite images and DSM data was found to be critical for effective correction.Mis-registration by one or two pixels could lead to large errors of retrieved surface reflectance factors in gully and ridge areas.Using low-resolution DSM data in conjunction with high-resolution satellite images will also fail to correct significant terrain components where they occur at the finer scales of the satellite images.DSM resolution appropriate to the resolution of satellite image and the roughness of the terrain is needed for effective results,and the rougher the terrain,the more critical will be the accurate registration.
基金This work was supported by the National Key Research and Development Program of China[grant number 2017YFC0803802]and the National Natural Science Foundation of China[grant number 41771486].
文摘Targeting at a reliable image matching of multiple remote sensing images for the generation of digital surface models,this paper presents a geometric-constrained multi-view image matching method,based on an energy minimization framework.By employing a geometrical constraint,the cost value of the energy function was calculated from multiple images,and the cost value was aggregated in an image space using a semi-global optimization approach.A homography transform parameter calculation method is proposed for fast calculation of projection pixel on each image when calculation cost values.It is based on the known interior orientation parameters,exterior orientation parameters,and a given elevation value.For an efficient and reliable processing of multiple remote sensing images,the proposed matching method was performed via a coarse-to-fine strategy through image pyramid.Three sets of airborne remote sensing images were used to evaluate the performance of the proposed method.Results reveal that the multi-view image matching can improve matching reliability.Moreover,the experimental results show that the proposed method performs better than traditional methods.
基金This work was supported by the Scientific and Technical Research Council of Turkey(TUBITAK)[grant number 114Y671].
文摘One of the challenges of remote sensing and computer vision lies in the three-dimensional(3-D)reconstruction of individual trees by using automated methods through very high-resolution(VHR)data sets.However,a successful and complete 3-D reconstruction relies on precise delineation of the trees in two dimensions.In this paper,we present an original approach to detect and delineate citrus trees using unmanned aerial vehicles based on photogrammetric digital surface models(DSMs).The symmetry of the citrus trees in a DSM is handled by an orientationbased radial symmetry transform which is computed in a unique way.Next,we propose an efficient strategy to accurately build influence regions of each tree,and then we delineate individual citrus trees through active contours by taking into account the influence region of each canopy.We also present two efficient strategies to filter out erroneously detected canopy regions without having any height thresholds.Experiments are carried out on eight test DSMs composed of different types of citrus orchards with varying densities and canopy sizes.Extensive comparisons to the state-of-the-art approaches reveal that our proposed approach provides superior detection and delineation performances through supporting a nice balance between precision and recall measures.
基金the National Natural Science Foundation of China(No.41401391)the Fundamental Research Funds for the Central Universities of China(No.2014YB071)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,and the Exclusive Talent Funds of Northwest A&F University of China(No.2013BSJJ017).
文摘Accurate data acquisition and analysis to obtain crop canopy information are critical steps to understand plant growth dynamics and to assess the potential impacts of biotic or abiotic stresses on plant development.A versatile and easy to use monitoring system will allow researchers and growers to improve the follow-up management strategies within farms once potential problems have been detected.This study reviewed existing remote sensing platforms and relevant information applied to crops and specifically grapevines to equip a simple Unmanned Aerial Vehicle(UAV)using a visible high definition RGB camera.The objective of the proposed Unmanned Aerial System(UAS)was to implement a Digital Surface Model(DSM)in order to obtain accurate information about the affected or missing grapevines that can be attributed to potential biotic or abiotic stress effects.The analysis process started with a three-dimensional(3D)reconstruction from the RGB images collected from grapevines using the UAS and the Structure from Motion(SfM)technique to obtain the DSM applied on a per-plant basis.Then,the DSM was expressed as greyscale images according to the halftone technique to finally extract the information of affected and missing grapevines using computer vision algorithms based on canopy cover measurement and classification.To validate the automated method proposed,each grapevine row was visually inspected within the study area.The inspection was then compared to the digital assessment using the proposed UAS in order to validate calculations of affected and missing grapevines for the whole studied vineyard.Results showed that the percentage of affected and missing grapevines was 9.5%and 7.3%,respectively from the area studied.Therefore,for this specific study,the abiotic stress that affected the experimental vineyard(frost)impacted a total of 16.8%of plants.This study provided a new method for automatically surveying affected or missing grapevines in the field and an evaluation tool for plant growth conditions,which can be implemented for other uses such as canopy management,irrigation scheduling and other precision agricultural applications.
基金This study was supported by the National Key Research and Development Program of China(No.2017YFD0700402)the Key Science and Technology Program of Shaanxi Province,China(No.S2016YFNY0066)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education MinistryPart of this research was supported by the Digital Viticulture program funded by the University of Melbourne’s Networked Society Institute,Australia.
文摘Information about canopy vigor and growth are critical to assess the potential impacts of biotic or abiotic stresses on plant development.By implementing a Digital Surface Model(DSM)to imagery obtained using Unmanned Aerial Vehicles(UAV),it is possible to filter canopy information effectively based on height,which provides an efficient method to discriminate canopy from soil and lower vegetation such as weeds or cover crops.This paper describes a method based on the DSM to assess canopy growth(CG)as well as missing plants from a kiwifruit orchard on a plant-by-plant scale.The DSM was initially extracted from the overlapping RGB aerial imagery acquired over the kiwifruit orchard using the Structure from Motion(SfM)algorithm.An adaptive threshold algorithm was implemented using the height difference between soil/lower plants and kiwifruit canopies to identify plants and extract canopy information on a non-regular surface.Furthermore,a customized algorithm was developed to discriminate single kiwifruit plants automatically,which allowed the estimation of individual canopy cover fractions(fc).By applying differential fc thresholding,four categories of the CG were determined automatically:(i)missing plants;(ii)low vigor;(iii)moderate vigor;and(iv)vigorous.Results were validated by a detailed visual inspection on the ground,which rendered an overall accuracy of 89.5%for the method proposed to assess CG at the plant-by-plant level.Specifically,the accuracies for CG category(i)-(iv)were 94.1%,85.1%,86.7%,and 88.0%,respectively.The proposed method showed also to be appropriate to filter out weeds and other smaller non-plant materials which are extremely difficult to be distinguished by common colour thresholding or edge identification methods.
基金theNationalNaturalScienceFoundationofChina (No 40 2 0 1 0 35)
文摘Segmentation and edge regulation are studied deeply to extract buildings fromDSM data produced in this paper. Building segmentation is the first step to extract buildings, anda new segmentation method-adaptive iterative segmentation considering rati-o mean square-is proposedto extract the contour of buildings effectively. A sub-image (such as 50X50 pixels) of the image isprocessed in sequence, the average gray level and its ratio mean square are calculated first, thenthreshold of the sub-image is selected by using iterative threshold segmentation. The current pixelis segmented according to the threshold, the average gray level and the ratio mean square of thesub-image. The edge points of the building are grouped according to the azimuth of neighbor points,and then the optimal azimuth of the points that belong to the same group can be calculated by usingline interpolation.
基金Funded by the Open Researeh Fund Program of the Geomatics and Applications Laboratory,Liaoning Technical University(No.2004010).
文摘In photogrammetry and remote sensing,image matching is a basic and crucial process for automatic DEM generation.In this paper we presented a image relaxation matching method based on feature points.This method can be considered as an extention of regular grid point based matching.It avoids the shortcome of grid point based matching.For example,with this method,we can avoid low or even no texture area where errors frequently appear in cross correlaton matching.In the mean while,it makes full use of some mature techniques such as probability relaxation,image pyramid and the like which have already been successfully used in grid point matching process.Application of the technique to DEM generaton in different regions proved that it is more reasonable and reliable.
基金Supported by the National Natural Science Foundation of China (Nos. 40771176, 40721001)
文摘A novel method for multi-image matching by synthesizing image and object-space information is proposed. Firstly, four levels of image pyramids are generated according to the rule that the next pyramid level is generated from the previous level using the average gray values of the 3 by 3 pixels, and the first level of pyramid image is generated from the original image. The initial horizontal parallaxes between the reference image and each searching image are calculated at the highest level of the image pyramid. Secondly, corresponding image points are searched in each stereo image pair from the third level of image pyramid, and the matching results in all stereo pairs are integrated in the object space, by which the mismatched image points can be eliminated and more accurate spatial information can be obtained for the subsequent pyramid image matching. The matching method based on correlation coefficient with geometric constraints and global relaxation matching is introduced in the process of image matching. Finally, the feasibility of the method proposed in this paper is verified by the experiments using a set of digital frame aerial images with big overlap. Compared with the traditional image matching method with two images, the accuracy of the digital surface model (DSM) generated using the proposed method shows that the multiimage matching method can eliminate the mismatched points effectively and can improve the matching success rate significantly.
基金Under the auspices of National Natural Science Foundation of China(No.41201464,41471316)Priority Academic Program Development of Jiangsu Higher Education Institutions(No.164320H101)
文摘Planation surface, a surface that is almost flat, is a kind of low-relief landforms. Planation surface is the consequence of the denudation and planation processes under a tectonic stable condition. The quantitative expression of the characteristics of planation surface plays a key role in reconstructing and describing the evolutionary process of landforms. In this study, Landform Planation Index(LPI), a new terrain derivative, was proposed to quantify the characteristics of planation surface. The LPIs were calculated based on the summit surfaces formed according to the clustering results of peaks. Ten typical areas in the Ordos Platform located in the central part of the Loess Plateau of China are chosen as the test areas for investigating their planation characteristics with the LPI. The experimental results indicate that the LPI can be effectively used to quantify the characteristics of planation surfaces. In addition, the LPI can be further used to depict the patterns of spatial differentiation in the Ordos Platform. Although the present Ordos Platform area is full of the high-density gullies, its planation characteristics is found to be well preserved. Furthermore, the characteristics of the planation surfaces can also reflect the original morphology of the Ordos Platform before the loess dusts deposition process evolved in this area. The statistical results of the LPI show that there is a gradually increasing tendency along with the increasing of slope gradient of summit surface. It indicates that the characteristics of planation surfaces vary among test areas with different landforms. These findings help to deepen the understanding of planation characteristics of the loess landform and its underlying paleotopography. Results of this study can be also served as an important theoretical reference value for revealing the evolutionary process of loess landform.
文摘The growing demand for current and precise geographic information that pertains to urban areas has given rise to a significant interest in digital surface models that exhibit a high level of detail. Traditional methods for creating digital surface models are insufficient to reflect the details of earth’s features. These models only represent three-dimensional objects in a single texture and fail to offer a realistic depiction of the real world. Furthermore, the need for current and precise geographic information regarding urban areas has been increasing significantly. This study proposes a new technique to address this problem, which involves integrating remote sensing, Geographic Information Systems (GIS), and Architecture Environment software environments to generate a detailed three-dimensional model. The processing of this study starts with: 1) Downloading high-resolution satellite imagery; 2) Collecting ground truth datasets from fieldwork; 3) Imaging nose removing; 4) Generating a Two-dimensional Model to create a digital surface model in GIS using the extracted building outlines; 5) Converting the model into multi-patch layers to construct a 3D model for each object separately. The results show that the 3D model obtained through this method is highly detailed and effective for various applications, including environmental studies, urban development, expansion planning, and shape understanding tasks.
